The present invention is directed to a display system for displaying selectable predetermined patterns on a cathode ray tube (CRT). Specifically, the disclosed system is directed to a pattern display system for use in conjunction with musical composition wherein musical notation and indicia indicative of musical composition are displayed on a CRT.
Digital display systems for displaying data from a source of digital information such as a computer are well known. Typically, such systems generally include a central processing unit for performing data processing tasks, such as the input and output of digital data, as well as the storage of digital data in some form of storage such as tape, disk, or core memory. Information is generally entered into the system through a keyboard, a punched card reader, or some other form of permanent storage which is machine readable. Generally, in such prior art systems, data is displayed on a cathode ray tube through the use of storage circuitry and display circuitry for appropriately retrieving stored information for display.
For example, a read-only memory can be utilized to provide character generation in response to being accessed through the use of code words. Such read-only memory systems can be used to display standard alphanumeric characters or predefined characters for special uses. An example of such a video display system is shown in U.S. Pat. No. 4,075,620, issued to Passavant et al. on Feb. 21, 1978, which is entitled VIDEO DISPLAY SYSTEM. U.S. Pat. No. 4,054,868, issued to Rose on Oct. 18, 1977, entitled ELECTRONIC MUSICAL SCALE AND CHORD DISPLAY APPARATUS, discloses a display apparatus which utilizes programmable read-only memories to control light emitting diode display elements, and is not directed to CRT display systems.
However, prior art CRT display systems are generally complicated, requiring extensive storage for data representative of each character displayed and storage output buffers. Further, prior art character display systems provide for the display and characters only in pre-defined character regions on the CRT display area, thus limiting the choice of locations where characters can be placed.
It is, therefore, an object of the disclosed invention to provide a CRT display system which does not require extensive data storage.
A further object of the invention is to provide a CRT pattern display system wherein pattern location is accurately and variably defined.
Still a further object of the invention is to provide a CRT display system which is particularly suited to display characters whose meaning is determined by vertical position on the display.
Another object of the disclosed invention is to provide an improved CRT display system wherein the circuitry for providing video signals includes read-only memories for providing display information in response to pattern information and timing information.
A further object of the invention is to provide an improved CRT display system wherein the timing operations for providing the video signals are relatively simple.